1. Field of the Invention
The present invention relates to the field of semiconductor integrated circuits and more specifically to a depleted substrate transistor (DST) and its method of fabrication.
2. Discussion of Related Art
Modern integrated circuits today are made up of literally hundreds of millions of transistors integrated together into functional circuits. In order to further increase the computational power of logic integrated circuits, the density and performance of the transistors must be further increased and the operating voltage (Vcc) further reduced. In order to increase device performance and reduce operating voltages, silicon on insulator (SOI) transistors have been proposed for the fabrication of modem integrated circuits. Fully depleted SOI transistors have been proposed as transistor structure to take advantage of the ideal subthreshold gradients for optimized on current/off current ratios. That is, an advantage of SOI transistors is that they experience lower leakage currents thereby enabling lower operating voltage for the transistor. Lowering the operating voltage of the transistor enables low power, high performance integrated circuits to be fabricated. FIG. 1 illustrates a standard fully depleted silicon on Insulator (SOI) transistor 100. SOI transistor 100 includes a single crystalline silicon substrate 102 having an insulating layer 104, such as buried oxide formed thereon. A single crystalline silicon body 106 is formed on the insulating layer 104. A gate dielectric layer 108 is formed on a single crystalline silicon body 106 and a gate electrode 110 formed on gate dielectric 108. Source 112 and drain 114 regions are formed in the silicon body 106 along laterally opposite sides of the gate electrode 110. Unfortunately, the amount of gate oxide scaling and gate length scaling that can be reliably and uniformly achieved with today's structures and processes is becoming limited.
Thus, what is desired is a novel transistor structure which enables further Vcc scaling and improved electrical performance.